Manual Pages  — RARPD

The rarpd utility services Reverse ARP requests on the Ethernet connected to interface. Upon receiving a request, rarpd maps the target hardware address to an IP address via its name, which must be present in both the ethers(5) and hosts(5) databases. If a host does not exist in both databases, the translation cannot proceed and a reply will not be sent.

By default, a request is honored only if the server (i.e., the host that rarpd is running on) can "boot" the target; that is, a file or directory matching the glob /tftpboot/ipaddr* exists, where ipaddr is the target IP address in hex. For example, the IP address 204.216.27.18 will be replied to if any of /tftpboot/CCD81B12, /tftpboot/CCD81B12.SUN3, or /tftpboot/CCD81B12-boot exist. This requirement can be overridden with the -s flag (see below).

In normal operation, rarpd forks a copy of itself and runs in the background. Anomalies and errors are reported via syslog(3).

The following options are available:

-a
	Listen on all the Ethernets attached to the system. If -a is omitted, an interface must be specified.
-d
	If -f is also specified, rarpd logs messages to stdout and stderr instead of via syslog(3).
-f
	Run in the foreground.
-P
	Specify the pathname of the PID file. If not specified, /var/run/rarpd.pid or /var/run/rarpd.ifname.pid will be used depending on the -a flag or the specified interface name.
-s
	Supply a response to any RARP request for which an ethernet to IP address mapping exists; do not depend on the existence of /tftpboot/ipaddr*.
-t
	Supply an alternate tftp root directory to /tftpboot, similar to the -s option of tftpd(8). This permits rarpd to selectively respond to RARP requests, but use an alternate directory for IP checking.
-v
	Enable verbose syslogging.

bpf(4)

Finlayson, R., Mann, T., Mogul, J.C., Theimer, M., 4 p, RFC 903: Reverse Address Resolution Protocol, June 1984.

The rarpd utility can depend on the DNS to resolve the name discovered from /etc/ethers. If this name is not in the DNS but is in /etc/hosts, the DNS lookup can cause a delayed RARP response, so in this situation it is recommended to configure nsswitch.conf(5) to read /etc/hosts first.